Bi-directional replication for the same MySQL table

Question

AppA stores/retrieves data from dbA.tableA AppB stores/retrieves data from dbB.tableA

tableA definition is the same across these databases. To start with dbB.tableA was copied from dbA.tableA (assuming both had 5 rows).

row6 was created by AppA (say primary key 6) row7 was created by AppB (say primary key 7)

I would like row7 to be copied to dbA.tableA and row6 to dbB.tableA

1. Is this even possible to setup bi-directional replication, so that the AppA, AppB view the same data at any point in time.
2. If the primary key is an auto-increment, would it be possible to maintain integrity of data or is there a possibility that there would be collisions on the primary key.

Answer 1

I'm assuming these are different instances of MySQL (most likely on different servers).

You can set up Master-master replication, where dbA is a master of dbB and vice versa.

Then, to avoid auto-increment collisions, set the following in my.cnf on dbA:

auto_increment_increment=2
auto_increment_offset=1

And the following on dbB:

auto_increment_increment=2
auto_increment_offset=2